A keyboard apparatus is a signal input apparatus inputting a relevant signal to a host side directly by way of depressing a certain key button out of the plurality of key buttons disposed in a predetermined positional relationship on a board in the electronic equipment. Although there have been various keyboard apparatuses proposed with different key switch structure with respect to each other, all of those keyboards perform the same function.
Namely, the key switches each are provided with a key button mounted thereon, wherein it is adapted such that depression of a certain key button out of the plurality of key buttons disposed on the board causes a movable contact in the key switch to come in contact with a fixed contact in a lower position of the key switch, and the contact between the movable contact and the fixed contact allows the keyed information signal to be output to the host side to operate the electronic equipment.
For example of this key board apparatus, U.S. Pat. No. 4,677,600 discloses the key switch structure being used of plate spring serving as an elastic member for contacting the movable contact to the fixed contact in the switch and separating the movable contact from the fixed contact. In addition to the plate spring, an elastic member such as a coil spring, a rubber spring and the like was proposed and has been used as an element of the general key switch structure.
The conventional keyboard apparatus generally has a problem that the structure of the key switch is very complicated. Particularly, since a key stem portion depresses the elastic member directly to move the movable contact into contact with the fixed contact in the key switch and a key top portion for allowing depression by a finger of a operator are mechanically separated from each other in the conventional type of apparatus. Thus, the number of the switch component parts is increased accordingly and thereby the production cost is expensive.
Also, since it is generally impossible to insert directly a key button into a key holder from the upper side after the key holder has been assembled into a frame of a keyboard apparatus in such a conventional type, the key stem portion of the key button should be inserted into the key holder before assembling the key holder. Therefore, the number of assembling steps is increased and it is not easy to automate the assembling process.
Moreover, since every key holders disposed on the conventional keyboard apparatus in predetermined positional relationship are separated from each other, it requires an additional key holder support to maintain the key holders on the keyboard and therefore the number of switch component part is increased.